Forex is often described as a 24-hour market, and from Sunday evening to Friday evening that is broadly true. But it is a five-day market, and the weekend break creates something currency traders need to understand: the gap. Today is Sunday, which makes it a good day to talk about it.
What a gap is
A gap occurs when the opening price of a new period is meaningfully different from the previous period’s closing price, with no trading in between at the prices in the middle. On a forex chart that is most visible at the Sunday open, when the first quote of the week can sit above or below Friday’s final quote.
The market is not literally shut. Banks and dealers in some centres still price over the weekend on a limited basis, and news continues to arrive. But the large interbank market stops streaming liquid prices, and retail brokers stop quoting. When quoting resumes, the first price reflects everything that happened in between.
Why gaps happen
- Weekend news. Elections, geopolitical events, central bank comments, or surprises in commodity markets can arrive while no one is trading. The Sunday open is the first chance to price them.
- Thin opening liquidity. In the first minutes after the open, few dealers are quoting, so spreads are wide and prices can jump between quotes.
- Risk repositioning. Participants who reduced exposure before the weekend may re-enter at the open, and those who held risk may close it.
- Scheduled risk. The week ahead may begin with major events early in the week, such as a cluster of central bank decisions, which can make participants cautious or aggressive from the first tick.
Most weeks the gap is small, often a few pips on major pairs, and it frequently closes within hours. But the distribution has fat tails. A few weekends a year produce large gaps, and those are the ones that hurt.
How a gap hits your stop-loss
This is the core risk for a retail trader. A stop-loss order is an instruction to close a position once the market trades at or beyond a given level. It is not a guarantee of the exit price. If the market opens beyond your stop, a standard stop order is triggered and then filled at the best available price, which can be well past the level you chose. This is gap slippage.
Here is an illustrative example. Suppose a trader is long a pair with a stop 40 pips below entry, risking 1% of the account. If the pair opens 100 pips beyond the stop, the realised loss may be roughly two and a half times the planned risk, around 2.5%. Nothing malfunctioned; the stop simply could not be filled in a price that did not trade. We covered the placement side of this in where to place a stop-loss.
Some brokers offer guaranteed stops, usually for a premium or a wider spread, and these do fill at the stated price. Check the terms carefully, including cost and conditions. Whether a feature exists is a question for your broker’s documentation, and our broker due diligence guide lists what to ask.
Gaps and position sizing
The honest way to handle gap risk is in your sizing rather than your hopes. If you hold positions over the weekend, your real risk is not the distance to the stop but the distance to the stop plus a plausible gap. Two practical approaches:
- Size for the gap. Reduce the position held over the weekend so that a larger-than-normal gap still stays within what you can tolerate. See position sizing and risk per trade.
- Flatten before the close. Many traders close or reduce positions on Friday afternoon. This has a cost: you may miss moves, and you pay spread on re-entry. It is a trade-off, not a rule.
Should you trade the gap?
Stock traders talk about “gap fills”, the idea that price tends to return to the prior close. In forex, small gaps do often retrace, but that is a tendency, not a law, and large gaps driven by real news may not fill for weeks. If you want to trade this idea, test it. Define the gap size, the entry, the stop and the exit before looking at results, and include the wide spreads of the first minutes of the week in your costs. Many apparent gap edges disappear once realistic spreads are applied, as discussed in spreads and slippage.
A lower-risk habit for most traders is simply to wait. The first 30 to 60 minutes after the Sunday open are typically the thinnest and most erratic. Letting liquidity build before you act removes a lot of avoidable cost.
A Sunday routine
- Check the weekend headlines and the calendar for the first two days of the week.
- Note Friday’s close for each pair you follow, so you can measure the gap objectively.
- Decide in advance what size of gap would change your plan, and what you will do.
- If you are already holding positions, look at where the gap would put your stops and what the loss would be.
- Do not chase the first print. Wide spreads at the open are a cost, not a signal.
Gaps are a reminder that a stop-loss is a risk-control tool with limits, not a ceiling on losses. Plan for the case where it does not fill where you expect, and you will rarely be surprised by one.
General education only; not trading advice. Numeric examples are illustrative.